The mechanical treatment of workpieces by means of, for example, cutting tools can be monitored by detecting structure-borne noise produced during the treatment in order to detect defects occurring during the treatment of the workpiece such as possibly crack formation in the workpiece or a tool fracture.
Such monitoring of the state or fracture of a tool or workpiece is known from DE 10 2006 023 716 B3. There a sound sensor is brought to rest flat against each of the two flat faces of a workpiece to be monitored. A drill fracture, for example, can be determined on the basis of a measurement of the difference between the transit times of sound signals to the two sound sensors. Here however, no particular requirements are imposed on the coupling of the sound sensor to the workpiece since merely the presence of a sound signal needs to be identified.
If the workpiece does not have any facilities for flat coupling for the sound sensor but rounded sections, a coupling element in the form of a scanning arm according to DE 94 03 901 U1 can be used for the point-by-point coupling of the sound sensor to the workpiece. A disadvantage here, however, is that the contact area of the sound sensor on the surface of the workpiece is small. This has the result that only a low acoustic power is transmitted from the workpiece to the sound sensor whilst the predominant fraction of the structure-borne noise power available for the evaluation remains unused.
In addition to the low transmitted acoustic power, however, the transmitted sound spectrum is limited in the case of merely point-by-point coupling and in DE 94 03 901 U1 is additionally possibly beset and falsified by interference signals due to a grinding contact.
Such a known point-by-point coupling is therefore not suitable for methods in which the sound emission spectrum overall is detected and evaluated. In particular when detecting the sound emission spectrum right up to very high frequency ranges, a merely point-by-point coupling proves to be unsuitable. A flat coupling of a sound sensor to round or stepped workpieces is, however, frequently impossible since the contact surfaces are not complementary.
An apparatus for non-destructive examination of test specimens using low-frequency sound signals is known from DE 10 2006 059 413 A1. An ultrasound transducer for low-frequency sound signals having a flexible membrane is known from U.S. Pat. No. 5,426,980 A. JP 08-0 21 828 A describes the use of cavities in a waveguide for damping sound waves. JP 2006-3 49 486 A discloses a sound sensor having a contact surface which is shaped complementary to the contact surface to be coupled.
Against this background, it is the object of the invention to provide a coupling element for acoustically coupling a sound transducer to a body for transmitting high-frequency structure-borne noise from the sound transducer to the body and/or from the body to the sound transducer and a sound transducer for detecting and/or producing high-frequency structure-borne noise during the mechanical treatment of workpieces by which means improved transmission of sound between a body on the one hand such as a mechanically treated workpiece or a tool and a sound sensor on the other hand is achieved.